This invention claims priority of the German patent application 100 42 272.1 filed Aug. 29, 2001 which is incorporated by reference herein.
The invention relates to a stand arrangement, in particular for medical examining and surgical microscopes.
Stands for medical examining and surgical microscopes are known to comprise a support foot and an upper part which cam be rotated with respect to the support foot about a first vertical axis and on which there is fastened a boom which can pivot about a horizontal axis and can be rotated about the first vertical axis and/or about a second vertical axis and serves the purpose of holding a microscope connected to it. It is further known to provide on the stand an illuminating system, having at least one lamp housing and at least one flexible optical conductor, for illuminating an object.
Stands for surgical microscopes must, on the one hand, be very mobile and capable of being effectively balanced so that the movement of the microscope can be performed with a low expenditure of force and in a very short time. On the other hand, the stand must be very stiff in order to permit a good image quality and to prevent shaking of the image. The relatively large overhang required by the boom for application on the operating table produces high forces and bending moments on the components and bearing points.
A relatively strong light source is required in order to illuminate the surgical site optimally. As a rule, this is integrated into a lamp housing designed as a separate component. In order for this lamp housing not to obstruct the surgeon during the operation, and also so that the heat radiated by the lamp housing does not hamper the surgeon, it is usual to arrange the lamp housing far away from the surgical microscope, for example on the support foot. The light is conducted to the surgical site by means of a flexible optical conductor. This arrangement of the lamp housing requires very long optical conductors. A very high degree of flexibility is required given that these optical conductors must be guided past the many joints of the stand.
One known stand design, the xe2x80x9cZeiss Visu 200 and S8xe2x80x9d, requires less flexibility. This design also has lazy tongs, which form the boom. The lazy tongs are spring-loaded by means of a bearing spring, and therefore permit balancing so that a user can operate a relatively counterbalanced microscope. In this case, xe2x80x9crelatively counterbalancedxe2x80x9d means that the user scarcely feels the weight of the microscope, because it is cancelled by the force of the bearing spring in the lazy tongs design. This apparent balancing is not, however, performed via weight equalization over a vertical axis of rotation or bearing axis of the stand. Rather, the load of the lazy tongs, and all the loads hanging from itxe2x80x94including, for example, the weight of the bearing spring and the microscope, together with accessory equipmentxe2x80x94are absorbed in the form of bending forces on the vertical bearing axis. These bending forces lead to a tilting moment which is, in turn, absorbed by a sufficiently large and heavy support foot below the vertical bearing axis.
The greater the loads, the greater the bending forces become, and the greater the tilting moments, the larger and heavier the support foot must be. However, the larger the support foot, the less freedom of movement there is for the user during his activity in the region of the stand.
WO 9901693 A1 discloses a microscope stand in the case of which this problem is solved by installing the control, illumination, etc. on the vertical bearing axis in a region projecting away from the microscope.
A certain balancing effect, or at least a displacement of the overall centroid in the direction of the vertical bearing axis may also be yielded by the abovementioned stand design of xe2x80x9cZeiss Visu 200 and S8xe2x80x9d. Changes to the weight of the microscope or its accessory equipment can, however, be compensated in the case of both known solutions only by changing the spring force of the bearing spring, that is to say all the changes in weight lead to a change in the balance about the vertical bearing axis and/or to changed bending moments on the latter.
It is the object of the invention to create a stand arrangement which can be kept more effectively in the balanced state of equilibrium via the vertical bearing axis without the need in this case to increase the total weight of the stand design.
In accordance with the invention, this is achieved by virtue of the fact that a carrier for holding the lamp housing is provided on the side diametrically opposite the boom with respect to the vertical axis. Since the carrier is arranged opposite the boom, the weight of the carrier and of the lamp housing, when multiplied by the distance of their centroids from the vertical pivoting axis, yields counter-moments which oppose the torques produced on the boom. In the optimum situation, the sums of these moments cancel one another out. The support foot can therefore be made smaller, and the total weight can be designed to be the same or even smaller.
The carrier is expediently rigidly connected to the boom. This produces a two-armed lever, corresponding to a balance beam which is mounted such that it can rotate about an axis and on which the individual forces can act. The carrier and the boom can be of unipartite design, or be assembled from at least two elements.
In order to be able to adapt to the various equipment configurations of the microscope, for example by adding on different accessory parts, the lamp housing is advantageously arranged on the carrier such that it can be displaced and fixed. This displaceability can occur, for example, in stages by means of rows of holes for the fastening screws, or continuously by means of longitudinal slots.
In the simplest design, the boom can pivot on the upper part about the vertical axis of rotation of the support foot. However, it is expedient for a universal adjustability of the stand that the boom can pivot on the upper part about an axis running parallel to the vertical axis of rotation of the support foot. It is thereby possible for an intermediate link between the support foot and the boom, or upper part forming the carrier, to be pivoted away quickly if required. In this case, the upper part can be of unipartite or multipartite design.
The lamp housing containing the transformer, the incandescent bulbs and any required controllers is normally not very heavy. Consequently, in accordance with a development of the invention, fastening means for holding additional balance weights are provided on the carrier and/or on the lamp housing for more effective balancing of the stand. Such fastening means can be, for example, guide bars on which the balance weights can be displaced and fixed as in the case of a balance beam.
Instead of, or in addition to, balance weights, it is advantageous to provide spring means for balancing between the carrier and the upper part. Such spring means can be designed, for example, as simple tension springs or as gas-pressure springs. By using them, it is possible to make the bearing spring, possibly provided on the boom, smaller, and thereby reduce the weight of the boom itself, and this in turn assists the balancing effect.
The displacement of the lamp housing and/or of the balance weights can be performed purely manually by scales or by feel. However, this procedure requires expenditure of time and a certain degree of experience or skill. However, it can occur during an operation that accessory parts of different weight and centroid distance need to be exchanged very quickly. In order that no delays or complications occur in this case, in accordance with a development of the invention, the displacement of the lamp housing and/or of the balance weights is advantageously performed via an automatic controller, as a function of the position and/or the weight of the microscope and/or its accessory equipment. The controller can be regulated, for example, via force sensors, deformation sensors, displacement sensors or angle sensors. It is also possible in this case for external forces, for example a person leaning against the stand, to be compensated.
A device for automatically balancing a stand is specified in a plurality of exemplary embodiments in U.S. Pat. No. 6,129,319 (based on WO 9713997 A1), such patent being hereby incorporated by reference into the present specification. The automatic functions for automatically balancing a stand are illustrated and described in FIGS. 1 to 6, 8 and 18 to 20 and the associated description.